In buildings or enclosures, it is desirable to provide windows and doors which allow natural light to enter the building or enclosure which is to be shielded from electromagnetic radiation, such as microwave radiation, yet the window units should be heat insulating while being transparent to visible light. Such buildings or enclosures might be used for housing digital computers or sensitive electronic equipment which could be adversely affected by high or low level radiation in the range from kilohertz frequencies to gigahertz frequencies. Moreover, there exists a security basis in many government and military buildings for shielding the interiors thereof to prevent electronic eavesdropping. The ability to remotely access information through electronic monitoring can be significantly reduced by the use of electronic shielding techniques when combined with properly designed shielded walls, roofs and floors.
Glass panes with electrically conductive films applied directly thereto have been used in the past. However, they have not been used to shield a space from the effects of electromagnetic radiation in certain wavelength ranges.
Until now, there has been no suitable glass unit which allows for shielding yet still allows for the entrance of natural light through a continuous field of vision while insulating from loss or gain of heat within the interior of a building. In the prior art, the use of metal mesh screens fails to allow for continuous viewing through the shielding membrane. Because of this drawback, a need has existed for an improved glass unit which not only serves as a window or door unit but also provides a shield for electromagnetic radiation which would otherwise penetrate the building. The present invention satisfies this need.